North Korea says it is considering readjusting the timing of the launch of a long-range rocket originally scheduled to take off between December 10 and 22.

The official KCNA state news agency said Saturday its technicians are "carefully contemplating ways to readjust the timing of launching" the rocket, because a series of problems arose in the process.

An American research organization said North Korea's preparations for a planned rocket launch may have been delayed by heavy snow.

The U.S.-Korea Institute at Johns Hopkins University said new satellite imagery suggests preparations at the Sohai satellite launch station are proceeding "more slowly than previously reported."

Japan said Thursday it is deploying its missile defense system in anticipation of North Korea's planned rocket launch, which, as currently scheduled, could occur as early as Monday.

Japanese television showed three Aegis destroyers armed with SM-3 missile interceptors reportedly headed for the East China Sea and the Sea of Japan.

Patriot missile interceptors later arrived at Okinawa island, which lies under the missile's projected flight path. Patriot missiles were also positioned behind the defense ministry in Tokyo.

Pyongyang announced last week that it would launch the rocket, supposedly to put a satellite in orbit. Its neighbors and much of the rest of the world have warned against the launch, saying it is really a disguised missile test and banned under U.N. sanctions.

Japan had threatened to shoot down the North Korean missile if it goes off course.

The U.N. Security Council condemned a failed North Korean launch in April, during which the rocket disintegrated shortly after takeoff.

Attempted North Korean rocket launches ended in failure in both 2006 and 2009, although North Korea claimed success.